Microbes can be social. In some groups of microbes that have parasitic lifecycles the social behavior of the many microbial cells can lead to the precise control of the animal they infect. The microbes orchestrate within the body and coordinate to form interactions that are as impressive as any other collective behavior from fish shoals to flocks of birds to ant trails. In some biological systems the manipulated animal is an ant and therefore belongs to its own collective, the colony. In our system we study the `zombie-ant' fungi (Ophiocordyceps) of tropical and temperate forests, which precisely control ants to leave their nest and bite into vegetation directly over the foraging trails of the colony. The function of such altered behavior becomes apparent when the fungus kills the ant and grows a stalk from its head that shoots out spores that infect other ants. The goal of this application is o develop models of such complex collective behavior by fungi controlling ants. We will develop computational and physical diffusion models of the development of the fungal collective, within its ant host. We will use high throughput Scanning Electron Microscopy of ant muscles and computer vision algorithms to develop 3D computational models and accurate networks of cells. We will perform micro-acoustic fluidic experiments to measure fungal behavior and develop physical diffusion models of the emergence of collective behavior. At the macroscopic scale we will measure infected ant behavior in the forest and build agent-based models to determine the rules explaining the effective targeting of ant trails by the fungal collective using the ant as a vehicle. Finally, we will perform experiments to understand the role of competition for the social behavior of microbes. This work is a collaboration among David Hughes, an expert of animal behavior and parasites, Ephraim Hanks, an expert on models of animal behavior, Danny Chen, a computer scientist expert in 3D models of cells, Francesco Costanzo, a theoretical mechanical expert in physical diffusion models and Tony Huang, an engineer expert in micro-acoustic fluidic experiments. Extensive collaboration already exists among the five researchers and four of the five occupy the same building at Penn State, ensuring an easy collaboration.